To provide a shutter mechanism for camera capable of opening/closing a shutter blade after switching a diaphragm in accordance with subject luminance with a simple constitution.

When a shutter button 27 is somewhat pressed in, a release lever 77 turns to a photometry starting position. At such a time, a pressing piece 77d turns on a photometric switch 44 so as to measure the subject luminance. When the subject luminance is lower than a specified level, a solenoid 69 is turned on so that the diaphragm is switched. Furthermore, when the button 27 is pressed in deeply, the lever 77 is turned to a release start position. At such a time, the locking projection 78c of a winding stop lever 78 is separated from a projection 79b, and a shutter driving lever 79 turns counterclockwise. Thus, a kick arm 79c kicks the abutting part 51b of the shutter blade 51 rightward so as to open/close a shutter aperture 50a. The shutter blade is opened/ closed after switching the diaphragm in accordance with the subject luminance.